Two-speed hydraulic control system

ABSTRACT

A backhoe having a stick cylinder and bucket cylinder selectively operable with a hydraulic control system having separate pumps to supply hydraulic fluid under pressure to the stick and bucket cylinders. Each pump delivers hydraulic fluid to a primary valve which gives the pump priority to a single cylinder. A second valve is operable to combine the hydraulic fluid output from both pumps to a single cylinder, thereby increasing the speed of operation of the cylinder. When both cylinders are operated at the same time, each cylinder receives the hydraulic fluid from its priority pump. An air control system, operable with high and low air pressure, is used to selectively operate the hydraulic control system.

States ate 1.

[54] TWO-SPEED HYDRAULIC CONTROL SYSTEM [72] lnventor: Charles W. Wienke, North St. Paul, Minn.

[73] Assignee: American Hoist & Derrick Company, St.

Paul, Minn.

[22] Filed: Nov. 12, 1969 [21] Appl. No.: 875,746

[52] US. CL ..91/6, 91/461 [51] Int. Cl ....F01b 25/02, F15b 9/03 [58] FieldofSearch ..91/463,6,461,14-1,363

[56] References Cited UNITED STATES PATENTS 2,613,650 10/1952 Mott ..91/363 2,356,366 8/1944 Wise.... ..91/461 2,988,881 6/1961 Reggie l ..91/141 3,038,449 6/1962 Murphy et a]. ..91/6

[ 5] Feb. 15,1972

FOREIGN PATENTS OR APPLICATIONS 972,080 10/1964 England ..9l/6 941,041 3/1956 Germany ..91/6

Primary ExaminerEdgar W. Geoghegan Assistant Examiner-Clemens Schlmikowski AttorneyBurd, Braddock & Bartz [57] ABSTRACT A backhoe having a stick cylinder and bucket cylinder selectively operable with a hydraulic control system having separate pumps to supply hydraulic fluid-under pressure to the stick and bucket cylinders. Each pump delivers hydraulic fluid to a primary valve which gives the pump priority to a single cylinder. A second valve is operable to combine the hydraulic fluid output from both pumps to a single cylinder, thereby increasing the speed of operation of the cylinder. When both cylinders are operated at the same time, each cylinder receives the hydraulic fluid from its priority pump. An air control system, operable with high and low air pressure, is used to selectively operate the hydraulic control system.

9 Claims, 3 Drawing Figures SHEET 1 OF 2 j a4 INVENTOR. CHARLES M Al/E/VKE A fro/PM! Y3 PATENTEDFEB 15 m2 SHEET 2 OF 2 TWO-SPEED HYDRAULIC CONTROL SYSTEM BAC KGROUN D OF INVENTION The hydraulic controls for a backhoe material handling machine have a common source of fluid under pressure. This fluid is used to operate the stick cylinder, as well as the bucket cylinder. The speed of operation of these cylinders is a function of the pressure and volume of fluid available to the cylinders. Normally, the pressure and volume of the fluid supply is relatively constant. When both cylinders are operated at the same time, the fluid supply is divided, thereby reducing the effectiveness of both cylinders. This fluid supply does not allow for change in the speed of operation of the cylinders without considerable loss of energy or an increase in the horsepower required to establish the fluid pressure.

SUMMARY OF INVENTION The invention relates to a fluid control system to operate a fluid motor, as a hydraulic ram or cylinder, at least at two different speeds. The system uses separate pumps to supply fluid under pressure to each fluid motor. A valve means, fluidly coupled to the pumps and motor, is sequentially operable to first connect one pump to a single fluid motor and to sequentially connect more than one pump to the single fluid motor to increase the speed of operation of the fluid motor. The valve means may be actuated with force-applying means having a first force to operate the valve means to couple one pump with one cylinder and a second force to operate the valve means to couple more than one pump with the one cylinder. The second force is greater than the first force and overrides and blocks out the first force.

IN THE DRAWINGS FIG. 1 is a side view of a backhoe having the fluid control system of the invention;

FIG. 2 is a diagrammatic view of the fluid control system of the invention; and

FIG. 3 is a modification of the fluid control system of the invention.

Referring to the drawings, there is shown in FIG. 1 a material-handling machine, commonly known as a backhoe, used for trenching and other excavating operations. Machine has a track assembly 11 carrying a horizontal deck 12. Pivotally mounted on the forward portion ofthe deck 12 is an elongated boom 13. A stick 14 is movably mounted on the end of the boom 13 with a transverse pivot member 16. The elevation of both the boom 13 and stick 14 is controlled with cables 17 connected to a hoist 18 mounted on the deck 12. The deck 12 also carries the controls and operator cab (not shown), as well as the engine for driving the hoist l8 and track assembly 11. The cable 17 is trained over a sheave assembly 19. The sheave assembly 19 is mounted on the top of an upright support 21. The cables 17 are secured to both the boom 13 and stick 14 at points where the action is such that when the stick 14 and boom 13 are lowered, the stick 14 moves back in an upward direction as the boom 13 moves downwardly to compensate for the gain in depth caused by the arc of the boom 13.

Pivotally mounted on the lower end of the stick 14 is a bucket 22 having rearwardly directed teeth 23 along the bottom of the mouth of the bucket. A transverse pivot member 24 pivotally connects the top of the bucket to the lower end of stick l4.

Pivotal movement of the stick 14 relative to the boom 13 is controlled with a double-acting hydraulic stick cylinder 26. The rear end of the cylinder housing is connected with a pivot 27 to a bracket on the middle section of the top of the boom 13. The rod portion of the cylinder 26 is connected to the upper end of the stick 14 with a pivot 28. The pivotal movement of the bucket 22 relative to the stick 14 is controlled with a double-acting hydraulic bucket cylinder 29. The upper end of the cylinder 29 is connected to a bracket on the upper front portion of the stick 14 with a transverse pivot 31. The lower end of the bucket cylinder 29 is connected to a toggle linkage 32 with an intermediate pivot 33. One portion, or link. of the toggle linkage is connected to the back of the bucket 22. The other portion of the toggle linkage is pivotally connected to the lower end of the stick 14. The hydraulic cylinders 26 and 29 control the position of the bucket 22 relative to the material to be removed from the hole or excavation 34. For effective digging and filling of the bucket 22, it is important that the bucket 22 is maintained at the correct pitch. Tilting the bucket 22 too far back causes the bucket to take, and rolling the bucket too far ahead causes the engine to power out. The correct pitch of the bucket 22 is normally found by experimentation and practice with the controls for the cylinders 26 and 29.

The control system shown in FIG. 2 and indicated generally at 36 for the stick cylinder 26 and bucket cylinder 29 is operative to selectively utilize the output of a multiplicity of hydraulic pumps to operate one or both of the hydraulic cylinders through a unique arrangement and control of hydraulic valves. The control system 36 has a pair of pumps 37 and 38 providing a separate hydraulic fluid supply, as oil, to each cylinder 26 and 29. The pumps 37 and 38 may be a double pump driven ofi" of the engine mounted on the deck 12. Pump 37 draws hydraulic fluid from a reservoir 39 and discharges the fluid under pressure into a line 41 leading to a first or primary spool valve 42. Valve 42 has a linear movable three-positioned spool which is normally closed in the central position. The flow directions of the valve 42 are indicated by the arrows. A spring 43, located around the valve actuator 42A, biases the spool of the valve to the normally closed position. Valve 42 is connected to the head end and rod end of the cylinder 26 with lines 44 and 46, respectively. Return line 47 connects valve 42 with reservoir 39.

Pump 38 withdraws hydraulic fluid from the reservoir 39 and discharges the hydraulic fluid into a line 48 connected to a primary spool valve 49. The valve 49 has a linear movable three-positioned spool which is biased into its central neutral position with a spring 51 located around the valve actuator 49A. The flow directions of the valve 49 are indicated by the arrows. Valve 49 is connected to the head and rod ends of bucket cylinder 29 with lines 52 and 53. A return line 54 connects the valve 49 with the reservoir 39. The pumps 37 and 38 are also separately connected to a pair of secondary valves 56 and 57 operable to selectively supply each cylinder with a second source of hydraulic fluid under pressure and thereby increase the speed of the cylinder. If both cylinders are used at the same time, each receives hydraulic fluid from its priority pump.

Valve 56 has a linear movable spool which is in the central closed or blocked position by the action of a spring 58. The valve 57 has a linear movable spool having a central closed position maintained by a spring 59. The pump 38 is connected to a line 61 to deliver fluid under pressure to the valve 56. The valve 56 is also connected to a return line 62 leading to the reservoir 39. The pump 37 is connected to a supply line 63 connected to the valve 57. The valve 57 is also connected to the return line 62. A first link 64 is pivotally connected to the ends of the spool actuators of the valves 42 and 56. In the same manner, a second link 66 is connected to the spool actuators of the valves 49 and 57. A force applying means or valve control means, indicated generally at 67, is operable to selectively operate or concurrently operate the pairs of valves 42, 56, and 49, 57, whereby each of the cylinders 26 and 29 operate at either a slow speed or a fast speed in both the expanding and the contracting motions of the cylinders.

Valve control means 67 comprises a first air cylinder 68 having a movable rod 69 connected with a pin 71 in an offset or unbalanced relationship to the link 64. The distance between the pin 71 and the valve actuator 42A is shorter than the distance between the pin 71 and valve actuator 56A so that the valve 42 will always be operated before valve 56. Upon actuation of the air cylinder 68, the valve 42 will move before and with less force than the valve 56. This directs fluid from primary pump 37 to the cylinder 26. Fluid from seconda- 'ry pump 38 is not directed to cylinder 29 until valve 56 is moved with additional force from the air cylinder 68.

A second air cylinder 72 is operatively connected in an unbalanced relationship to the valves 49 and 57. Second air cylinder 72 has a movable rod 73 joined in an unbalanced relationship with a pivot 74 to the link 66. The pin 74 is located close to the valve actuator 49A. The distance between pivot pin 74 and the valve actuator 49A is shorter than the distance between pin 74 and valve actuator 57A so that valve 49 will always be operated before valve 57. A first air thumb valve 76 is connected with lines 78 and 79 to the air cylinder 68. In a similar manner, a second air thumb valve 77 is connected with lines 81 and 82 to the air cylinder 72. The air thumb valves 76 and 77 are operable to normally vent the air from opposite sides of the cylinders, supply air to the cylinders to move the rods 69 and 73 in a forward direction, and move the rods 69 and 73 in a rear direction. The thumb valves 76 and 77 are connected to an air supply 83 so that upon operation of the thumb valves, air will be supplied to the air cylinders 68 and 72, as determined by the operator of the machine. The line 84 between the air supply 33 and the thumb valves 76 and 77 has a first or low air pressure regulator 86 and a second or high air pressure regulator 87. The low-pressure regulator 86 is connected through a check valve 88 and line 89 to a common line 91 for supplying air to both thumb valves 76 and 77. The high-pressure regulator 87 is connected through a shutoff cock 92 to the line 91.

In use, the air regulator 86 can be set at 45 p.s.i. and the air regulator 87 can be set at 85 psi. The shutoff cock is operative, in a first position, to block the 85-p.s.i. air so that the air regulator 86 can supply air through the check valve 88 into the line 91 leading the thumb valves 76 and 77. With the lowpressure air supplied to the thumb valves, actuation of the thumb valves will only actuate valves 42 and 49 so that the pump 37 will only supply hydraulic fluid to the cylinder 26 and the pump 38 will only supply hydraulic fluid to the cylinder 29. The low air pressure in the air cylinders 68 and 72 is only sufficient to compress the springs 43 and 51 to actuate the spools in the valves 42 and 49.

When the shutoff cock 92 is moved to the open position, the air pressure regulator 87 supplies the high-pressure air to the line 91. The check valve 88 prevents the air from escaping through the low-pressure regulator 86. The high-pressure air is supplied to both thumb valves 76 and 77. When the thumb valves are actuated, the highressure air is supplied to the air cylinders 68 and 72. This high-pressure valve is sufficient to overcome the biasing forces of the springs 58 and 59 of the third and fourth valves 56 and 57. When valve 42 is closed, pump 37 is operative to supply hydraulic fluid under pressure to the bucket cylinder 29 upon actuation of the air cylinder 72 with high air pressure. When air cylinder 72 is actuated, pump 38 supplies fluid to cylinder 27. Since valve 49 is actuated before valve 57, pump 38 supplies fluid to the cylinder before pump 37 adds to the supply of fluid to the cylinder. This sequential supply of fluid to the cylinder reduces fluid shock loads on the fluid system. In a similar manner, pump 38 is operative to supply oil under pressure through the valve 56 to the stick cylinder 26, in addition to the oil being supplied by pump 37.

This twovolume oil supply arrangement allows a change in speed of the operation of the cylinders 26 and 29 without turning the excess energy created by the pumps into heat or using additional horsepower. The control system contains a separate control for separate functions of the cylinders 26 and 29. Each pump has a priority for a single cylinder. When one of the cylinders is not operated, its pump may be utilized for an additional hydraulic supply for the second cylinder.

Upon operation of the unbalanced linkage systems 64 and 66, the primary valves 42 and 49 are actuated first, thereby providing the cylinders 26 and 29 with a fluid under pressure. When the secondary valves 56 and 57 are subsequently actuated, the additional hydraulic fluid does not create a hydraulic shock because the hydraulic fluid from the second pump is introduced into the fluid lines for the cylinder after the first pump is supplying fluid to the cylinder.

Referring to FIG. 2, there is shown a modification of the two-speed control system for a hydraulic double-acting cylinder 93. The control system, indicated generally at 94, comprises a primary valve 96 and a secondary valve 97. Valve 96 has a linear movable spool, with the flow patterns indicated by arrows and a spool actuator 98. Valve 97 is similar in structure, having a spool with flow patterns indicated by arrows and a valve actuator 99. A link 101 is pivotally mounted to the ends of the actuators 98 and 99. The spool in valve 96 is normally biased to a central neutral closed position with a spring 102 located about the actuator 98. In a similar manner, a spring 103 biases the spool of valve 97 to its central neutral position. A first pump 104 is connected with a line 106 to the valve 96. A return 107 carries return hydraulic fluid from the valve 96 to a reservoir 108. The hydraulic cylinder 93 is connected to the valve 96 with lines 109 and 111 so that upon ac tuation of the valve 96, the pump 104 will direct fluid to one end of the cylinder, with the fluid at the opposite end of the cylinder returning to the reservoir 108.

A second pump 112 draws fluid from reservoir 108 and directs fluid under pressure into line 113 connected to the second valve 97. A return line 114 connects valve 97 with the reservoir 108. Lines and 115 couple valve 97 with lines 109 and 111 to carry fluid to cylinder 93.

The valves 96 and 97 are selectively operated with a control, indicated generally at 116. The control 116 is operative to first actuate the valve 96 to connect pump 104 to cylinder 93, and subsequently, actuate the valve 97 to increase the flow of hydraulic fluid to the cylinder 93 under the influence of the second pump 112. Control 116 comprises a lever 117 pivotally connected to a support 1 18. Lever 117 is connected to the link 101 with a bar member 119. Pivot pin 120 connects the bar 119 to the midportion of the lever 117. in a similar manner, a pivot pin 121 pivotally connects a bar member to the link 101. The pivot pin 121 is located in an offcenter or unbalanced relationship relative to the actuators 98 and 99. The pivot pin 121 is located closer to the actuator 98 than the actuator 99.

In operation, when the lever 117 is moved in the direction of the arrow 122, the lever will initially move the valve 96 from position 1 to position 2. Upon application of additional force to the lever, the bar 101 will move to position 3 and thereby actuate the valve 97. When both the valves 96 and 97 are actuated, both pumps 104 and 112 are operative to supply hydraulic fluid under pressure to the cylinder 93. When only the valve 96 is actuated, pump 104 is the sole source of hydraulic fluid for the cylinder 93. The control system 116 is operative to selectively utilize the outputs of the pumps 104 and 112 to operate the cylinder 93 at a slow speed or at a high speed. The unbalanced link 10] eliminates the hydraulic shock in the cylinder 93 because the valve 96 is actuated first to allow the pump 104 to supply fluid to the cylinder 93. Upon subsequent actuation of the valve 97, the pump 112 adds to the output of pump 104 to increase the flow of hydraulic fluid under pressure to the cylinder 93.

The invention has been described with respect to preferred embodiments of a hydraulic control system and valve control means for controlling the working speed of the cylinders. The unbalanced linkage systems for the valve means can be controlled by air or hydraulic cylinders, or electrically by the use of solenoids or other electromechanical equipment. The spool valves can have built-in pump relief and cylinder relief ports with anticavitation checks to protect the pumps and cylinders. Each hydraulic circuit to the cylinders can incorporate a counterbalance valve to prevent cavitation of the cylinders. The hydraulic fluid can be replaced with pneumatic fluid. Also, the fluid motors can be rotary-type motors.

The springs, operating the primary and secondary valves, can have different biasing strengths to provide for the sequential operation of the primary and secondary valves.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. ln combination: a fluid motor, a first pump, a second pump, a first valve connected to the first pump and fluid motor, said first valve having a first spool movable to a first position to direct fluid from the first pump to the fluid motor, a first actuator connected to the first spool, a second valve connected to the second pump and the fluid motor, said second valve having a second spool movable to a first position to direct fluid from the second pump to the fluid motor, a second actuator connected to the second spool, control means having common linkage means connected to the first actuator and the second actuator, first biasing means acting on a portion of the common linkage means to bias the first spool to a neutral position, second biasing means acting on another portion of the common linkage means to bias the second spool to a neutral position, and force applying means connected to the linkage means between the first biasing means and second biasing means for first operating the first spool to direct fluid from the first pump to the fluid motor in response to a first force to overcome the force of the first biasing means and, subsequently, operate the second spool in response to a second force greater than the first force to overcome the combined forces of the first and second biasing means to add fluid from the second pump to the fluid motor.

2. The combination of claim 1 wherein: the linkage means connected to the first actuator and the second actuator includes a link connected to both actuators, said force applying means connected to the link in an offcenter relation to operate the first spool before the second spool.

3. The structure of claim 1 wherein: the fluid motor is a double-acting cylinder connected to the first valve and the second valve.

4. The structure of claim 1 wherein: the force applying means is a manually operable linkage.

5. The structure of claim 1 wherein: the force applying means is an air cylinder, including a first air pressure regulator to provide the air cylinder with low-pressure air and a second pressure regulator to provide the air cylinder with high-pressure air and air control means to block the first pressure regulator when the second pressure regulator is providing highpressure air to the air cylinder.

6. The structure of claim 5 including: a thumb valve connected to each regulator and the air cylinder to control the flow of air to the air cylinder.

7. The structure of claim 5 wherein: the air control means includes a one-way valve to block the flow of high-pressure air into the first regulator from the second regulator and shutoff means to stop the flow of air from the second regulator.

8. In combination: a fluid motor, a plurality of separate pumps for supplying fluid under pressure, a plurality of valve means fluidly connecting the fluid motor with the pumps, said valve means operable to first connect one pump to the fluid motor and to subsequently connect more than one pump to said fluid motor, each valve means having a spool and an actuator connected to the spool, and control means having common linkage means connected to each actuator, separate biasing means acting on separate portions of the common linkage means to bias the spools to their neutral positions, and force applying means for first operating one spool to direct fluid from said one pump to the fluid motor in response to a first force sufficient to overcome the force of the biasing means associated with said one spool and, subsequently, operate another spool in response to a second force greater than the first force sufficient to overcome the forces of the biasing means acting on both said one spool and said another spool to add fluid from more than one pump to the fluid motor.

9. The structure of claim 8 wherein: the force applying means is an air cylinder which includes a first air pressure regulator to provide the air cylinder with low air pressure and a second pressure regulator to provide the air cylinder with high air pressure and air control means to block the first air pressure regulator when the second air pressure regulator is supplying high air pressure to the air cylinder. 

1. In combination: a fluid motor, a first pump, a second pump, a first valve connected to the first pump and fluid motor, said first valve having a first spool movable to a first position to direct fluid from the first pump to the fluid motor, a first actuator connected to the first spool, a second valve connected to the second pump and the fluid motor, said second valve having a second spool movable to a first position to direct fluid from the second pump to the fluid motor, a second actuator connected to the second spool, control means having common linkage means connected to the first actuator and the second actuator, first biasing means acting on a portion of the common linkage means to bias the first spool to a neutral position, second biasing means acting on another portion of the common linkage means to bias the second spool to a neutral position, and force applying means connected to the linkage means between the first biasing means and second biasing means for first operating the first spool to direct fluid from the first pump to the fluid motor in response to a first force to overcome the force of the first biasing means and, subsequently, operate the second spool in response to a second force greater than the first force to overcome the combined forces of the first and second biasing means to add fluid from the second pump to the fluid motor.
 2. The combination of claim 1 wherein: the linkage means connected to the first actuator and the second actuator includes a link connected to both actuators, said force applying means connected to the link in an offcenter relation to operate the first spool before the second spool.
 3. The structure of claim 1 wherein: the fluid motor is a double-acting cylinder connected to the first valve and the second valve.
 4. The structure of claim 1 wherein: the force applying means is a manually operable linkage.
 5. The structure of claim 1 wherein: the force applying means is an air cylinder, including a first air pressure regulator to provide the air cylinder with low-pressure air and a second pressure regulator to provide the air cylinder with high-pressure air and air control means to block the first pressure regulator when the second pressure regulator is providing high-pressure air to the air cylinder.
 6. The structure of claim 5 including: a thumb valve connected to each regulator and the air cylinder to control the flow of air to the air cylinder.
 7. The structure of claim 5 wherein: the air control means includes a one-way valve to block the flow of high-pressure air into the first regulator from the second regulator and shutoff means to stop the flow of air from the second regulator.
 8. In combination: a fluid motor, a plurality of separate pumps for supplying fluid under pressure, a plurality of valve means fluidly connecting the fluid motor with the pumps, said valve means operable to first connect one pump to the fluid motor and to subsequently connect more than one pump to said fluid motor, each valve means having a spool and an actuator connected to the spool, and control means having common linkage means connected to each actuator, separate biasing means acting on separate portions of the common linkage means to bias the spools to their neutral positions, and force applying means for first operating one spool to direct fluid from said one pump to the fluid motor in response to a first force sufficient to overcome the force of the biasing means associated with said one spool and, subsequently, operate another spool in response to a second force greater than the first force sufficient to overcome the forces of the biasing means acting on both said one spool and said another spool to add fluid from more than one pump to the fluid motor.
 9. The structure of claim 8 wherein: the force applying means is an air cylinder which includes a first air pressure regulator to provide the air cylinder with low air pressure and a second pressure regulator to provide the air cylinder with high air pressure and air control means to block the first air pressure regulator when the second air pressure regulator is supplying high air pressure to the air cylinder. 